1. Field of the Invention
The present invention relates to an apparatus for communicating with an RFID tag configured to perform information reading from an RFID tag capable of radio communication of information with an outside.
2. Description of the Related Art
A Radio Frequency Identification (hereinafter referred as RFID) system configured to transmit and receive information in a non-contact manner with an RFID tag storing information is known. The non-contact transmission and reception methods include an electromagnetic coupling method using a coil, an electromagnetic induction method, and a radio wave method, for example.
An RFID tag circuit element provided in an RFID tag has an IC circuit part and a tag antenna. The IC circuit part stores predetermined RFID tag information. The tag antenna is connected to the IC circuit part and performs information transmission and reception. If a transmission wave is transmitted from a transmission antenna of a reader/writer to the RFID tag, the RFID tag circuit element replies to the transmission wave. There has been a prior art reference for smooth communication with a plurality of RFID tags with regard to an apparatus for communicating with an RFID tag configured to conduct such communication.
The prior art reference is provided with a transmission circuit part capable of creating a carrier wave with a plurality of frequencies. Then, according to an environment in which the plurality of RFID tags are mounted, a switching circuit part selects a frequency hardly affected by the environment. The transmission circuit part generates the carrier wave at the selected frequency. As a result, reliable communication can be conducted with each of the plurality of RFID tags.
For example, a plurality of RFID tags constitute a small group, and a plurality of the small groups constitute a large group so that a relatively large number of RFID tags are present in general. In order to make a quick search in such situation, it is more efficient that a rough search is made for small groups to which the RFID tag belongs and then, the RFID tag as a search target is searched in the small group.
However, in the prior art reference, the above-described point is not given particular consideration. That is, even if the small group and the large group are formed as above, a switching circuit part selects a frequency corresponding to the RFID tag as a search target, and then, individual RFID tags belonging to the small group are searched. That is, fine searches are made from the beginning for individual RFID tags, and an efficient search for a targeted RFID tag has been difficult.